import { describe, expect, it } from "@suaveplan/testing/runner";
import type { Rng } from "@suaveplan/types";
import { weightedChoice } from "./sample.js";

class FakeFloatRng implements Rng {
    public constructor(protected value: number) {}
    public nextUint32(): number {
        return 0;
    }
    public nextFloat(): number {
        return this.value;
    }
}

describe("weightedChoice floating-point fallback", () => {
    it("returns last index when target >= total (FP edge)", {
        timeout: 5000,
    }, () => {
        // A nextFloat value of exactly 1 would make target === total,
        // so `target < acc` never fires and the function must fall through
        // to the defensive final return.
        const rng = new FakeFloatRng(1);
        const idx = weightedChoice([1, 2, 3], rng);
        expect(idx).toBe(2);
    });
});